Sheng H. Lin

Removal of heavy metals from aqueous solution by chelating resin in a multistage adsorption process

Copper and zinc removal from aqueous solution by chelating resin was investigated theoretically and experimentally in the present study. A multistage process was proposed as an alternative for enhancement of the heavy removal of the single-stage process. Heavy metal mass balance equations with empirical Freundlich adsorption isotherm were developed to represent the multistage process and the theoretical model permits determination of the inter-stage heavy metal concentrations and the total amount of chelating resin required for achieving a desired level of heavy metal removal. Optimization of the linearized theoretical model shows that equal division of the total amount of chelating resin among all stages of the multistage process yields the best results in terms of saving of chelating resin for a given heavy metal removal or enhanced heavy metal removal for a given total amount of chelating resin. Experimental tests were also conducted to establish the equilibrium adsorption of heavy metal by the chelating resin and to empirically verify the advantages of the multistage adsorption process.

Treatment of high-strength phenolic wastewater by a new two-step method.

Treatment of high-strength phenolic wastewater by a novel two-step method was investigated in the present study. The two-step treatment method consisted of chemical coagulation of the wastewater by metal chloride followed by further phenol reduction by resin adsorption. The present combined treatment was found to be highly efficient in removing the phenol concentration from the aqueous solution and was proved capable of lowering the initial phenol concentration from over 10,000 mg/l to below direct discharge level (1mg/l). In the experimental tests, appropriate conditions were identified for optimum treatment operation. Theoretical investigations were also performed for batch equilibrium adsorption and column adsorption of phenol by macroreticular resin. The empirical Freundlich isotherm was found to represent well the equilibrium phenol adsorption. The column model with appropriately identified model parameters could accurately predict the breakthrough times.

Combined physical, chemical and biological treatments of wastewater containing organics from a semiconductor plant.

Wastewater containing organics from a semiconductor plant was experimentally investigated in this study. The wastewater is characterized by strong color, high chemical oxygen demand (COD), a large amount of refractory volatile organic compounds and low biodegradability. Because of these characteristics, treatment of this wastewater by traditional activated sludge method is essentially impossible. In the present work, combined physical, chemical and biological methods were synergistically utilized to tackle the wastewater. The combined treatment consisted of air stripping, modified Fenton oxidation and sequencing batch reactor (SBR) method. Air stripping was employed to remove the majority of volatile organic components (notably isopropyl alcohol) from the wastewater, while the Fenton treatment decomposed the remaining refractory organics leading to simultaneous reductions of wastewater COD and color. After proper dilution with other low-strength, organics-containing wastewater stream, the wastewater effluent was finally treated by the SBR method. Experimental tests were conducted to determine the effectiveness and the optimum operating conditions of each treatment process. Test results clearly demonstrated the advantages of the combined treatments. The treatment train was found capable of lowering the wastewater COD concentration from as high as 80,000 mg/l to below 100mg/l and completely eliminating the wastewater color. The overall water quality of the final effluent exceeded the direct discharge standard and the effluent can even be considered for reuse.

Industrial wastewater treatment in a new gas-induced ozone reactor.

The present work was to investigate industrial wastewater treatment by ozonation in a new gas-induced reactor in conjunction with chemical coagulation pretreatment. The reactor was specifically designed in a fashion that gas induction was created on the liquid surface by the high-speed action of an impeller turbine inside a draft tube to maximize the ozone gas utilization. A new design feature of the present reactor system was a fixed granular activated carbon (GAC) bed packed in a circular compartment between the reactor wall and the shaft tube. The fixed GAC bed provided additional adsorption and catalytic degradation of organic pollutants. Combination of the fixed GAC bed and ozonation results in enhanced oxidation of organic pollutants. In addition to enhanced pollutant oxidation, ozonation was found to provide in situ GAC regeneration that was considered crucial in the present reaction system. Kinetic investigations were also made using a proposed complex kinetic model to elucidate the possible oxidation reaction mechanisms of the present gas-induced ozonation system. As a complementary measure, chemical coagulation pretreatment was found able to achieve up to 50% COD and 85% ADMI removal. Experimental tests were conducted to identify its optimum operating conditions.

Enhanced electrochemical oxidation of anionic surfactants

Abstract The surfactant wastewater treatment by electro‐chemical oxidation with or without peroxide hydrogen was investigated. The two anionic surfactants studied here were alkylbenzene sulfonate (ABS) and linear alkylbenzene sulfonate (LAS), both of them being widely used in the household and industrial detergents. Experiments were conducted to examine the effects of pH, electrolyte concentration, time of electrochemical oxidation, power input and amount of hydrogen peroxide (H2O2) on the surfactant removal and other water quality parameters. Optimum operating conditions were experimentally determined. The enhanced version of electrochemical oxidation (i.e. with addition of hydrogen peroxide) was found to be significantly more efficient than that without.

Adsorption of hydrazoic acid from aqueous solution by macroreticular resin

Sodium azide is a key component in the automobile air bag. When dissolved in aqueous solution, it reacts rapidly with water to form hydrazoic acid which is a highly toxic chemical and is strongly regulated by government. In the present study, adsorption of hydrazoic acid from aqueous solution by macroreticular resin is investigated. This method can provides a convenient means for dealing with the toxic hydrazoic acid. Experimental tests of batch equilibrium adsorption and continuous column adsorption of hydrazoic acid were conducted and the test results were employed to establish adsorption isotherm and to evaluate the column adsorption efficiency. The test results revealed that the multilayer adsorption isotherms, like the modified Langmuir or Jossens model, are needed to adequately describe the hydrazoic acid adsorption equilibrium between the liquid and solid (resin) phases. In the column adsorption process, a theoretical model was adopted for representing the hydrazoic acid change in the aqueous solution exiting the column and the verified theoretical model significantly facilitates prediction of adsorption breakthroughs and column design. Regeneration of exhausted resin was investigated. Solution of 10% (w/w) NaCl was found to be a very efficient regenerant.

Prediction and experimental verification of HFC‐134a adsorption by activated carbons

Abstract Theoretical and experimental investigations were conducted on the adsorption characteristics of 1,1,1,2‐tetrafluoroethane (HFC‐134a) by granular and extruded activated carbons (GAC and EAC). HFC‐134a is currently regarded as an excel‐lent replacement for CFC‐12 (Freon 12), a refrigerant previously used in all automobiles and many cooling systems. Experimental results of column adsorption were employed to verify the theoretical breakthrough curves generated from the pro‐posed model and excellent model fit of the breakthrough curves of HCFC‐134a adsorption were obtained. Investigations were also made on the effects of gas velocity, inlet HFC‐134a concentration and operating temperature on the adsorption efficiency.

A theoretical model for predicting column phenol adsorption by macroreticular resin

Abstract Theoretical and experimental investigations have been conducted on the adsorption characteristics of phenol by macroreticular resin. A theoretical model was proposed for describing the breakthrough curves of phenol adsor‐ption in the column. Two constant parameters were involved in this proposed model, that need to be estimated empirically using observed breakthrough data. The predictions using the model were compared with the experimental data of phenol adsorption. The results indicated that the model yields consis‐tently good predictions for all the test cases conducted in the present study. Investigations were also made on the effects of liquid velocity and inlet phenol concentration on the adsorption efficiency.

Performance characteristics of waste oil emulsion treatment by ultrafiltration

Abstract The present work was undertaken to investigate the treatment of waste drawing oil which is a high‐strength oil/water emulsion commonly used in the cable and wire manufacturings. A semi‐batch ultrafiltration (UF) process was employed to study the treatment process. Experiments were conducted to examine the treatment performance characteristics of the UF membranes of hydrophilic and hydrophobic types and of different pore sizes. The COD (chemical oxygen demand) and copper concentration removal, turbidity (NTU) improvement and conductivity reduction of the UF treatment were experimentally determined. An exponential equation was proposed to empirically correlate the permeate volume to the applied pressure, temperature and mixing speed and the correlation was verified by the observed data. The experimental results have shown that the UF treatment was highly efficient. The quality of the permeate from the UF treatment process was excellent which permits the permeate to be considered for potential reuse...